Explosive container with yieldable seal



June 1, 1965 s. F. FOSTER 3,135,340

EXPLOSIVE CONTAINER WITH YIELDABLE SEAL Filed Jan. 10, 1964 STEPHEN F FOSTER INVENTOR.

3,135,340 EXPLGSYVE CQNTAINER Vt 1TH YEELDABLE SEAL Stephen F. Foster, Hopatcong, NJ, assignor to Hercules Powder Company, Wilmington, Bah, a corporation of Delaware Fiied Jan. it), 1964, Ser. No. 337,939 18 Claims. (1. 1tl224) This invention relates to an explosive column assembly especially adapted for use in seismic operations and more particularly to an improved explosive column assembly and plastic containers therefor.

The explosives industry has for many years packaged explosives in paper, metal and plastic containers, all of which have been provided with various types of coupling means for forming an explosive column. On a commercial basis, only the paper and metal containers have found wide acceptance primarily due to the economic factors involved when using plastic. Paper containers have been most widely accepted in view of their versatility for handling both sensitive and insensitive explosives; however, paper containers require a considerable amount of waterproofing and wall thickness to insure a substantially rigid explosive column. Metal containers have been widely accepted in view of their strength, waterproofness and ease of providing coupling means therefor; however, they have been limited to the packaging of relatively insensi tive explosives in view of the hazards involved in packaging and sealing sensitive explosives in metal. Plastic containers have not heretofore been appreciably accepted in view of the economic factors mentioned although it has long been realized that the material possessed many advantages, particularly in respect to waterproofness and safety for the packaging of sensitive as well as insensitive explosives.

Therefore, it is a principal object of the present invention to provide plastic containers which may be manufactured in an economical manner and which containers may be assembled in a facile, efficient and economical manner. Moreover, a further object is to provide additional desirable features heretofore not available to the art such as placing the packaged explosive under compressive force during assembly where if the container is not properly filled or if the column tends to elongate, improved contact between adjacent explosive charges is insured with attendant consistency of propagation and rate. Still another object is to provide plastic containers which may be quickly interconnected and locked in place.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

Generally described, the present invention comprises an explosive column assembly having a plurality of substantially cylindrical blown plastic containers charged with explosive, each of said containers having an interruptively beaded male coupling with locking indentations and an end closure at one end and having an interruptively grooved female coupling with looking indentations and a yieldable seal adjacent the explosive at the other end, said containers being fractionally rotated and interconnected by said male and female couplings and locked by engagement of their respective indentations, and said containers having the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings. In a more specific aspect in accordance with the present invention, there is provided a container for explosives, adapted for interconnection with like containers to form an explosive column assembly, which comprises a thin-walled elongated substantially cylindrical blown plastic container having explosive disposed therein throughout the major length of the 3,1863% Patented .lune 1, E965 container and having a yieldable seal within the container adjacent the explosive, a male coupling and end closure on one end of the container, said male coupling having at least one peripheral bead interrupted by a plurality of longitudinal slots extending a substantial length of the male coupling, a female coupling on the other end of the container, said female coupling having a plurality of interrupted peripheral grooves compatible with the bead and the slots of the male coupling, and locking indentations associated with the male coupling and the female coupling whereby like containers of explosive may be interconnected by slidable and rotatable engagement of the beads and the grooves of the male and female couplings and looked upon engagement of their respective indentations to form an explosive column assembly having the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

A preferred embodiment of the invention has been chosen for pur oses of illustration and description and is shown in the accompanying drawings where reference symbols refer to like parts wherever they occur.

FIG. 1 is an elevational view of a container in accordance with the invention with a part thereof in section showing the yieldable seal and adjacent explosive within the container;

FIG. 2 is a sectional view taken along line 22 of FIG 1; and FIG. 3 is a fragmentary part elevational and part sectional view showing the interconnection of the containers of FIG. 1 to form an explosive column assembly.

With reference to the drawings, a thin-wall elongated blown plastic container 1 has an explosive 2 disposed therein throughout the major length of the container. A yieldable seal 3 is provided within the container 1 adjacent the explosive 2. A slightly tapered male coupling 4 with a convex end closure 5 are formed as a unitary structure in the thin wall at one end of the container 1 and the explosive 2 extends into the bottom of the coupling. The male coupling 4 has a peripheral bead 6 with no pitch near the lower end thereof which is interrupted by four equally spaced longitudinal slots 7 which extend a substantial length of the male coupling thus dividing the bead 6 into four equal segments. Positioned midway above each segment of the bead 6 are two female locking indentations 8. The upper side of the 'bead 6 has its surface at a right angle to the longitudinal axis of the container with its lower side at an angle of about sixty degrees. Similarly, the surface opposite the lower side of the bead is at a right angle and the surface opposite the upper side of the bead is at an angle of about sixty degrees. This arrangement forming the bead grooves 11 with the right angle surfaces and absence of pitch on the bead 6 insures durable interconnection of like containers in contrast to beveled surfaces and pitch where an assembly of containers would tend to unscrew when subjected to tension loads as imparted by their own weight. A female coupling 9 adapted to receive the male coupling of a like container is provided at the other end of the container 1. The female coupling 9 has four sets of two peripheral grooves each represented by it which grooves are compatible with the bead grooves 11 and the slots 7 of the male coupling 4. Positioned midway above each set of grooves it) are two male locking indentations 12 compatible to engage with the female locking indentations of a like container a hereinafter described.

Referring now more particularly to FIG. 3 depicting the interconnection of like container to form an assembly, 1a and its like parts represent a superjacent container and 1 and its like parts represent the su-bjacent container. The male coupling 4a of container 1a with alignment of the indentations 12 and grooves It? within the slots 7a is slidably inserted into the female coupling 9 of container 1 with the convex end closure a exerting a positive compressive force on the yieldable seal 3 and adjacent explosive 2 whereby the yieldable seal 3 is depressed. The slidable insertion of the male coupling 4a proceeds until the upper end wall .of the slots 7a engages the upper indentations 12 whereby it is stopped. The bead grooves 11a are now in register with the grooves and the containers 1 and 1a are rotated relative to each other whereupon the grooves engage each other and the male locking indentations 12 ride up out of the slots 7a and over the male coupling body 4a into locking engagement with the female locking indentations 8a with FIG. 3 illustrating the locked position. It will be appreciated that the thin plastic wall of the female coupling 9 is sufiiciently elastic to accommodate the tapered male coupling 4a at its upper end to give a tight water resistant fit as well as being sufficiently elastic to permit the male indentations 12 to ride up out of the slots 7a for locking engagement with the female indentations 3a.

Furthermore, it will be appreciated that a considerable bending moment can occur in the thin body plastic containers of this invention particularly when several containers are interconnected in a horizontal position and then lifted for insertion in a vertical borehole. To counteract unusual bending moment imparted to the body of the thin-wall container 1, a plurality of longitudinal reinforcing ribs 14 is spaced circumferentially about and substantially coextensive with that portion of the body of the container lying between the male coupling 4 and the female coupling 9. Additionally, a plurality of girth reinforcing ribs 15 is spaced along the length of the longitudinal ribs 14 to insure overall integrity of the body structure of the container 1 against deformation under various conditions of manufacture and field handling. It has been found that the longitudinal reinforcing ribs 14 should have a width of not more than the width of the areas 16 lying therebetween and that ordinarily five of the girth reinforcing ribs 11 spaced along the length of the longitudinal ribs give very satisfactory results for the average size of most commercial cartridges. Moreover, the. length of the slotted portion 7 of the male coupling 4 is cor related with the upper indentation 12 of the female coupling 9 to insure that in assembling a column of the containers 1, the convex end closure 5 of the male coupling exerts a positive compressive force on the yieldable seal 3 and adjacent explosive 2 of the female coupling of a like container. This insures a consistent propagating relationship with consistency of rate and quite advantageously is accomplished in the field at the time the explosive column is being readied for use. Moreover, a tight seal is effected as between adjacent containers as the female coupling being slightly elastic has its end maintained in tension as it is forced to accommodate the tapered upper portion of the male coupling.

The following example will serve to illustrate a commercially sized preferred embodiment of this invention. It is to be understood, however, that the scope of the invention is not limited thereby with respect to the specific structure or to the explosive charges utilized.

A series of thin-wall containers was formed by blowmolding high-density polyethylene having a density of 0.962 and a nominal melt index of 0.8 (I at 190 C.) These containers were molded in a split mold designed to yield the structure heretofore described and illustrated as a preferred embodiment of the invention. Approximate dimensions of the containers were 22%" overall length; 2 body diameter; sixteen reinforcing ribs 7 wide raised & around 2 diameter; male coupling 4%" long with convex end; slotted portion 1%" long, '%2" wide and deep; bead /4" long with grooves each side /2 c. to c. and deep; female indentations diameter and 7 deep; female coupling 4% long, grooved midportion of female coupling /2" c. to c. and

deep; male indentations diameter, & deep and slightly tapered and rounded; ribbed body portion 13 long. The ribbed body portion had five girth ribs 7 wide equally spaced with the exception of a midportion 4" long wherein three ribs were omitted to provide a smooth area for labeling. The wall thickness of the body of the container, including the female coupling, was approximately 40 mils, and the wall thickness of the male coupling was approximately 55 mils. Programming was used during the blow-molding process to obtain female couplings that were uniform in thickness and strength.

Each of these containers was charged with approximately 5 pounds of explosive composition consisting of 49.0% nitroglycerin, 1.5% nitrocotton, 36.0% sodium nitrate, 7.0% pulp, 3.0% coated cob meal,.2.0% starch, 0.5% bagasse and 1.0% chalk. This charge filled each container to a heightapproxirnately level with the girth rib adjacent the female coupling. A cupped polyethylene sealing disk approximately 25 mils thick was then placed over the explosive and snugly filled into the annular girth rib. The containers thus manufactured were tested and initiated under conventional field conditions as explosive column assemblies containing from two to ten containers in each assembly. The tests were satisfactory in all respects with additional advantages hereinafter set forth.

With reference to the foregoing, it will be appreciated that the containers of this invention may be formed from many of the plastic materials capable of being blown but that the economy of the material will largely dictate its use. Thus, although linear polyethylene is preferred and has been found highly satisfactory, polyolefins generally, and copolymers and alloys thereof and other materials such as ABS terpolymer, plasticized vinyl chloride, plasticized vinyl chloride-vinyl acetate copolymer and the like may be used. Also, it will be appreciated that in addition to the specific seismic explosive used in the example, other explosives of various types suitable for various other blasting purposes may be used such as generally, gelatins, dynamites, semigelatin dynamites, permissibles, safety explosives, slurry explosives, nitrocarbonitrates and the like. Moreover, distinct advantages inure when employing the present invention for aqueous slurry explosives which show only a 1" or 2" propagation gap under water, and for gelatin dynamites where under very high Water pressure, the propagation gap is markedly reduced as compared to that observed under low water pressure. Furthermore, in addition to the polyethylene yieldable seal used in the example, other plastics such as those set forth for the container body and nonplastic seals may beused including treated paper board, waxes, resins, water-proofing compounds, and the like. Also, the seal may be a plastic cup sealed around its lip and the shell body with a hot melt adhesive, or a wax such as parafiin, or resins or asphaltic compounds or the like Where extreme waterproofness is desired. The essential thing is that the seals should be yieldable in respect to deflection or in respect to sliding along the wall of the container or otherwise yielding so that compressive force is gently but firmly developed with close proximity assured as between adjacent container explosive charges. Still further, although one bead, four slots and two male and female indentations have been described in the preferred embodiment, variations in respect to these may be made such as, several beads, three or more slots, one male and female indentation or one longitudinal male and female indentation and the like. Moreover, although the reinforcing ribs have been described as raised, they may be obtained also by providing a constant body diameter with the areas such as 16 depressed, thusforrning ribs such as 14 and 15. Ordinarily, the explosive containers of this invention are made available in sizes from about 6 to about 36 inches in length and from about 1 to about 8 inches in diameter with the number of interconnected units dependent upon the specific service desired. Generally, for seismic work, not more than about units are used, and the 2%." x 22 /4" container herein specifically described has been found a popular size. In progressing to the larger sizes, an increase in the wall thickness of the plastic is, of course, necessary but, nevertheless, due to the blown feature and other structural features introduced by this invention, the wall thickness need be only slightly increased, not exceedin about 10 to 25%, thus retaining economical manufacture.

The additional advantages previously referred to in connection with the example and field tests are as follows relative to prior art paper containers since metal containers cannot be used for this type explosive: more explosive energy obtained through using plastic shells; an increased overall specific gravity, which, coupled with the plastic surface features, results in improved gripping surface and improved sinldng rate in drill mud, consequently reducing the need or poling of charges; shorter shell length per given wei ht of charge provides a more compact charge; the charges in soft. containers are easier to prime for the shooter by conventional means; a lock type, fractionally rotated positive coupling feature making assembly or disassembly a faster and simpler task; increased protection to the powder charge because the plastic is impervious to water; a plastic unit susceptible for use wherever paper containers or metallic containers formerly were preferred and in some instances necessary; improved loading in boreholes due to flexibility as the plastic assembly will yield and slide by obstructions; and a general purpose plastic unit which does not tend to disintegrate or rust internally in the presence of moisture or watercontaining explosives and does not tend to disintegrate or rust in the presence of moisture or water as externally encountered in water-containing boreholes and unsheltered storage.

From the foregoing, it will be evident to those skilled in the art that various modifications can be made or fol lowed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

What I claim and desire to protect by Letters Patent is:

1. A container for explosives adapted for interconnection with like containers to form an explosive column assembly, which comprises:

(a) a thin-wall elongated substantially cylindrical blown plastic container having explosive disposed therein throughout the major length of the container and having a yieldable seal within the container adjacent the explosive,

(b) a male coupling and end closure on one end of the container, said male coupling having at least one peripheral bead interrupted by a plurality of longitudinal slots extending a substantial length of the male coupling,

(c) a female coupling on the other end of the container, said female coupling having a plurality of interrupted peripheral grooves compatible with the bead and the slots of the male coupling, and

(d) locking indentations associated with the male cou pling and the female coupling and the end closure of said male coupling having protrusion means to contact and to force the yieldable seal of a like container into the explosive adjacent thereto so that like containers of explosive interconnected by slidable and then rotatable engagement of the beads and the grooves of the male and female couplings and locked upon engagement of their respective indentations form an explosive column assembly having the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

2. A container for explosives adapted for interconnection with like containers to form an explosive column assembly, which comprises:

(a) a thin-wall elongated substantially cylindrical blown plastic container having explosive disposed therein throughout the major length of the container and having a yieldable seal within the container adjacent the explosive,

(b) a male coupling and end closure on one end of the container, said male coupling having at least one peripheral bead interrupted by a plurality of longitudinal slots extending a substantial length of the male coupling,

(0) a female coupling on the other end of the container, said female coupling having a plurality of interrupted peripheral grooves compatible with the bead and the slots of the male coupling, and

(d) a plurality of longitudinal reinforcing ribs spaced circumferentially about the substantially coextensive with that portion of the body of the container lying between the male coupling and the female coupling, and

(e) locking indentations associated with the male coupling and the female coupling and the end closure of said male coupling having protrusion means to contact and to force the yieldable seal of a like container into the explosive adjacent thereto so that like containers of explosive interconnected by slidable and then rotatable engagement of the beads and the grooves of the male and female couplings and locked upon engagement of their respective indentations form an explosive column assembly having the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

3. A container for explosives adapted for interconnection with like containers to form an explosive column assembly, which comprises:

(a) a thin-Wall elongated substantially cylindrical blown plastic container having explosive disposed therein throughout the major length of the container and having a yieldable seal within the container adjacent the explosive,

(b) a male coupling and end closure on one end of the container, said male coupling having at least one peripheral bead interrupted by a plurality of longitudinal slots extending a substantial length of the male coupling,

(c) a female coupling on the other end of the container, said female coupling having a plurality of interrupted peripheral grooves compatible with the bead and the slots of the male coupling, and

(d) a plurality of longitudinal reinforcing ribs spaced circumferentially about and substantially coextensive with that portion of the body of the container lying between the male coupling and the female coupling,

(e) a plurality of girth reinforcing ribs spaced along the length of the longitudinal reinforcing ribs, and

(f) locking indentations associated with the male coupling and the female coupling and the end closure of said male coupling having protrusion means to contact and to force the yieldable seal of a like container into the explosive adjacent thereto so that like containers of explosive interconnected by slidable and then rotatable engagement of the beads and the grooves of the male and female coupling and locked upon engagement of their respective indentations form an explosive column assembly having the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

4. A container for explosives adapted for interconnection with like containers to form an explosive column assembly, which comprises:

(a) a thin-wall elongated blown polyethylene plastic container having explosive disposed therein throughout the major length of the container and having a yieldable seal within the container adjacent the explosive,

(b) a male coupling and convex end closure on one end of the container, said male coupling having at least one peripheral bead interrupted by a plurality of longitudinal slots extending a substantial length of the male coupling,

(c) a female coupling on the other end of the container, said female coupling having a plurality of interrupted peripheral grooves compatible with the bead and the slots of the male coupling, and

(d) a plurality of longitudinal reinforcing ribs spaced circumferentially about and substantially coextensive with that portion of the body of the container lying between the male coupling and the female coupling,

(e) a plurality of girth reinforcing ribs spaced along the length of the longitudinal reinforcing ribs, and

(f) locking indentations associated with the male coupling and the female coupling and the end closure of said male coupling having protrusion means to contact and to force the yieldable seal of a like container into the explosive adjacent thereto so that like containers of explosive interconnected by slidable and then rotatable engagement of the beads and the grooves of the male and female couplings and locked upon engagement of their respective indentations form an explosive column assembly having the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

5. The explosive cartridge according to claim 4 wherein the longitudinal reinforcing ribs have a Width of not more than the width of the areas lying therebetween.

6. The explosive cartridge according to claim 4 wherein the blown polyethylene plastic is high-density polyethylene characterized by a density of 0.962 and a nominal melt index of 0.8.

7. An explosive column assembly comprising:

(a) a plurality of substantially cylindrical blown plastic containers charged with explosive,

(h) each of said containers having an interruptively beaded male coupling with locking indentations and a projected end closure having protrusion means at one end and having an interruptively grooved female coupling with locking indentations and a yieldable seal adjacent the explosive at the other end,

(c) said containers being fractionally rotated and interconnected by said male and female couplings and locked by engagement of their respective indentations, and

((1) said containers having the protrusion means of the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

8. An explosive column assembly comprising:

(a) a plurality of longitudinally reinforced substantially cylindrical blown plastic containers charged with explosive,

a (b) each of said containers having an interruptively beaded male coupling With locking indentations and a projected end closure having protrusion means at one end and having an interruptively grooved female coupling with locking indentations and a yieldable seal adjacent the explosive at the other end,

(c) said containers being fractionally rotated and interconnected by said male and female couplings and locked by engagement of their respective indentations, and

(d) said containers having the protrusions means of the end closures of the male couplings exerting cornpressive force on the yieldable seals and adjacent explosive of the female couplings.

9. An explosive column assembly comprising:

(a) a plurality of longitudinally and transversely reinforced substantially cylindrical blown plastic containers charged with explosive,

(b) each of said containers having an interruptively' beaded male coupling with locking indentations and a projected end closure having protrusion means at one end and having an interruptively grooved female coupling with locking indentations and a yieldable seal adjacent the explosive at the other end,

(0) said containers being fractionally rotated and interconnected by said male and female couplings and locked by engagement of their respective indentations, and

((1) said containers having the protrusion means of the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

10. The explosive column assembly according to claim 9 wherein the'plastic is high-density polyethylene characterized by a density of 0.962 and a nominal melt index References Cited by the Examiner UNITED STATES PATENTS 788,200 4/05 Finch 285--402 949,778 2/ 10 Pringle 1022l.6 1,037,709 9/12 Zieg 285401 1,940,657 12/33 Woodford 102-43 2,049,290 7/3 6 Burns et al. 285-401 2,345,887 4/44 Rothrock 102-24 2,857,844 10/5 8 Lagemann 10224 FOREIGN PATENTS 21, 845 10/96 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,186,340 June 1, 1965 Stephen F. Foster It is hereby certified that error appears in the above numbered patent reqliring correction and that the said Letters Patent should read as correctedbelow.

Column 4, line 21, for "filled" read fitted column 6, line 15, for "the" read and line 62, for "coupling read couplings column 7, line 41 strike out "a projected";

column 8, lines 6 and 24, strike out "a projected", each occurrence; same column 8, line 14, for "protrusions" read protrusion Signed and sealed this 19th day of October 1965.

SEAL) est:

NEST W. SWIDER EDWARD J. BRENNER :sting Officer Commissioner of Patents 

1. A CONTAINER FOR EXPLOSIVES ADAPTED FOR INTERCONNECTION WITH LIKE CONTAINERS TO FORM AN EXPLOSIVE COLUMN ASSEMBLY, WHICH COMPRISES: (A) A THIN-WALL ELONGATED SUBSTANTIALLY CYLINDRICAL BLOWN PLASTIC CONTAINER HAVING EXPLOSIVE DISPOSED THEREIN THROUGHOUT THE MAJOR LENGTH OF THE CONTAINER AND HAVING A YIELDABLE SEAL WITHIN THE CONTAINER ADJACENT THE EXPLOSIVE, (B) A MALE COUPLING AND END CLOSURE ON ONE END OF THE CONTAINER, SAID MALE COUPLING HAVING AT LEAST ONE PERIPHERAL BEAD INTERRUPTED BY A PLURALITY OF LONGITUDINAL SLOTS EXTENDING A SUBSTANTIAL LENGTH OF THE MALE COUPLING, (C) A FEMALE COUPLING ON THE OTHER END OF THE CONTAINER, SAID FEMALE COUPLING HAVING A PLURALITY OF INTERRUPTED PERIPHERAL GROOVES COMPATIBLE WITH THE BEAD AND THE SLOTS OF THE MALE COUPLING, AND (D) LOCKING INDENTATIONS ASSOCIATED WITH THE MALE COUPLING AND THE FEMALE COUPLING AND THE END CLOSURE OF SAID MALE COUPLING HAVING PROTRUSION MEANS TO CONTACT AND TO FORCE THE YIELDABLE SEAL OF A LIKE CONTAINER INTO THE EXPLOSIVE ADJACENT THERETO SO THAT LIKE CONTAINERS OF EXPLOSIVE INTERCONNECTED BY SLIDABLE AND THEN ROTATABLE ENGAGEMENT OF THE BEADS AND THE GROOVES OF THE MALE AND FEMALE COUPLINGS AND LOCKED UPON ENGAGEMENT OF THEIR RESPECTIVE INDENTATIONS FORM AN EXPLOSIVE COLUMN ASSEMBLY HAVING THE END CLOSURES OF THE MALE COUPLINGS EXERTING COMPRESSIVE FORCE ON THE YIELDABLE SEALS AND ADJACENT EXPLOSIVE OF THE FEMALE COUPLINGS. 